Knowledge of the particular composition and structure of the sea floor in a particular area, or along particular paths on the sea floor, can be extremely valuable information. For instance, knowledge of the soil composition of the sea floor, to include the surface of the sea floor and the upper layer of the sea floor to a depth of approximately three or four feet, can be extremely helpful in selecting sites for underwater structures and determining workable routes for cable and pipe line locations.
One currently used method for testing the physical characteristics of the sea floor is accomplished by using an acoustic doppler penetrometer. A penetrometer is essentially a projectile-shaped body which carries an acoustic signal transmitter. In operation, a penetrometer is dropped into the water from a surface vessel or an aircraft, and allowed to attain its terminal velocity before impacting the sea floor. A remote receiver analyses the doppler effect on the acoustic signal which results as the penetrometer impacts and penetrates into the sea floor. Such a penetrometer is disclosed in U.S. Pat. No. 4,007,633 which issued to Thompson for an invention entitled "Method of Determining the Physical Characteristics of a Sea Floor."
As will be readily appreciated, the sea floor at different locations can have many different compositions, to include sand, clay and rock. Also, the sea floor will vary greatly in its depth from the surface of the sea. Depending on the depth of the sea floor at a particular location, and the particular composition of the sea floor at that location, different penetrometer configurations may be required to obtain the most reliable and accurate signals indicative of the sea floor characteristics at the location.
One variable in the construction of a penetrometer is its weight as this parameter effects hydrodynamic performances. Very heavy penetrometers may be necessary for test sites having particularly firm sea floor surface material. Heavier penetrometers, however, are not required for softer surface materials. Accordingly, not all penetrometers need to weigh the same. Further, different penetrometer configurations may require different configurations for fin assemblies to stabilize their descent toward the sea floor. Accordingly, not all penetrometers require the same hydrodynamic control surfaces. It also happens that for harder, firm, sea floor conditions, longer penetrometers having smaller impact surfaces may be desirable. Accordingly, not all penetrometers need to have the same shape and length.
The present invention recognizes that penetrometer configurations must necessarily vary in order to create the most efficient penetrometer profile and penetrometer structure for effective testing of the sea floor's physical characteristics. Further, the present invention recognizes that with the ability to selectively configure the most efficient penetrometer profile and penetrometer structure, while at sea over the test site, cost savings can be realized. Specifically, these cost savings can be realized through a significant reduction in the amount of different material components required.
In light of the above, it is an object of the present invention to provide a penetrometer which can effectively generate an acoustic signal that can be processed to provide data indicative of the sea floor at the point where the penetrometer impacts the sea floor. Another object of the present invention is to provide a penetrometer which can be selectively configured as to weight, profile, and hydrodynamic control surfaces, according to the anticipated condition of the sea floor at the test site. Yet another object of the present invention is to provide a penetrometer which will provide an effective fluid tight seal for the required electronic componentry. Still another object of the present invention is to provide a penetrometer which is simple to use, relatively easy to manufacture, and comparatively cost effective.